package com.test.crc;

import com.google.common.base.Strings;
import com.test.utils.NumberUtils;

/**
 * 计算法CRC8测试工具类
 * 二项式：X^8+X^2+X^1+1 0b100000111 0x107
 */
public class Crc8Utils {

    private static Integer BINOMIAL = 0x107; // 0b100000111

    private static int[] crc8Table = new int[]{
            0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A, 0x2D,
            0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53, 0x5A, 0x5D,
            0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4, 0xC3, 0xCA, 0xCD,
            0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1, 0xB4, 0xB3, 0xBA, 0xBD,
            0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1, 0xF6, 0xE3, 0xE4, 0xED, 0xEA,
            0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88, 0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A,
            0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F, 0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A,
            0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42, 0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A,
            0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B, 0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4,
            0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2, 0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4,
            0x69, 0x6E, 0x67, 0x60, 0x75, 0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44,
            0x19, 0x1E, 0x17, 0x10, 0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34,
            0x4E, 0x49, 0x40, 0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63,
            0x3E, 0x39, 0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13,
            0xAE, 0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
            0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4, 0xF3
    };

    /**
     * 查表法计算CRC8
     *
     * @param bs
     * @return
     */
    public static Integer tableCrc8(byte[] bs) {
        Integer crc = 0x00;
        for (byte b : bs) {
            crc = crc ^ (b & 0xff);
            crc = crc8Table[crc];
//            System.out.println(crc);
        }
        return crc;
    }

    /**
     * 计算比特数组的CRC8值
     *
     * @param bs
     * @return
     */
    public static Integer crc8(byte[] bs) {
        Integer crc = 0x00;
        for (byte b : bs) {
            crc = crc ^ (b & 0xff);
            crc = calcCrc8(crc);
        }
        return crc;
    }

    /**
     * 计算数字的CRC8值，直接计算法
     * 二项式：X^8+X^2+X^1+1 0b100000111 0x107
     * 1、校验第8位是否为1。
     * 1.1、第8位是1，如果为1则左移一位，正好为9位，跟二项式位数一样，做异或。
     * 1.2、第8位不是1，则左移一位，继续循环。
     * 此流程正好是模2除法取余的正向计算方式
     *
     * @return
     */
    public static Integer calcCrc8(Integer num) {
        //        System.out.println(String.format("num=%s", num2Bin(num)));
        Integer crc = num;
        for (int i = 0; i < 8; i++) {
            if ((crc & 0x80) > 0) {
                crc = (crc << 1) ^ BINOMIAL;
            } else {
                crc = crc << 1;
            }
//            String strCrc = num2Bin(crc);
//            System.out.println(String.format("times=%s, result=%s, num=%s, len=%s", i + 1, strCrc, crc, strCrc.length()));
        }
        return crc;
    }

    public static void generateCrc8Tabel() {
        StringBuilder sb = new StringBuilder();
        sb.append("private static int[] crc8Table = new int[]{\n");
        for (int i = 0; i < 256; i++) {
            int x = calcCrc8(i);
            String ss = "0x" + Strings.padStart(NumberUtils.num2Hex(x).toUpperCase(), 2, '0');
            sb.append(ss);
            if (i != 256 - 1) {
                sb.append(", ");
            }
            if ((i + 1) % 16 == 0) {
                sb.append("\n");
            }
        }
        sb.append("};");
        System.out.println(sb.toString());
    }

}
